VMware GSX 3 - Manual (Page 200)

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200
VMware GSX Server Administration Guide
Using SCSI Reservation to Share SCSI
Disks with Virtual Machines
GSX Server permits the sharing of a preallocated virtual disk with multiple virtual
machines running on the same host, provided the disk in question is a SCSI disk.
When the disk is shared, all virtual machines connected to the disk use the SCSI
reservation protocol to write to the disk concurrently.
Clustering software must be installed in each virtual machine that intends to share a
SCSI disk. Enabling SCSI reservation in and of itself does not automatically mean that a
running virtual machine is a participant in the SCSI reservation protocol.
Note: Although growable virtual disks and physical disks can be used with SCSI
reservation, such use is considered experimental and should not be attempted in a
production environment. Only the use of preallocated virtual disks is fully supported
with SCSI reservation. When you create a new virtual machine, or add a new virtual
disk to an existing virtual machine, GSX Server creates a preallocated virtual disk by
default.
Note: This feature is advanced; use it only if you are familiar with SCSI in general and
the SCSI reservation protocol in particular.
The following sections describe how to use SCSI reservation to share disks among
multiple virtual machines.
• SCSI Reservation Support on page 200
• Enabling SCSI Reservation on page 201
• Issues to Consider When Sharing Disks on page 202
SCSI Reservation Support
SCSI reservation support is limited by the following:
• You can enable SCSI reservation for SCSI virtual and physical disks. No other type
of SCSI devices can use SCSI reservation in a virtual machine. Specifically, you
cannot enable SCSI reservation for a SCSI disk that is configured as a generic SCSI
device. For more information about generic SCSI, see
Connecting to a Generic
SCSI Device in the VMware GSX Server Virtual Machine Guide.
Note: VMware supports SCSI reservation when used with preallocated virtual
disks. Support for SCSI reservation with growable virtual disks and physical disks
is considered experimental. For high-availability configurations, use SCSI
reservation with preallocated virtual disks.